Radio-frequency identifier (RFID) methods are widely used in a number of applications, including smart cards, item tracking in manufacturing, inventory management in retail, etc. An RFID tag can be attached, e.g., to an inventory item. An EIR terminal can be configured to read the memory of an RFID tag attached to an inventory item.
EIR terminals with integrated RFID reading capabilities can read RFID tags from a range of distances and various terminal orientations with respect to an RFID tag being read. When an EIR terminal comprising an RFID reader is configured to display a scan trace, it provides the EIR terminal's operator with a visual feedback with respect to the scanning progress. At any moment in time, the RF signal coverage emitted by an EIR terminal can be defined by a 3D shape. The form and size of the 3D shape defining the RF signal coverage depends, among other factors, on the orientation of the EIR terminal, the RFID transmit power level, and the number and configuration of the RF antennas employed by the EIR terminal. Hence, a target scan area by an EIR terminal can be visualized as a projection of the 3D RF signal coverage shape onto an arbitrarily chosen plane.
For a moving EIR terminal, a visual scan trace can be provided by different graphical representations such as a solid line, continuous line, or a dotted line, each line defined by a multitude of time varying points, each point being a projection of the 3D RF signal coverage shape onto the arbitrarily chosen plane at a given moment in time. The imaginary plane onto which the visual scan trace is projected can be chosen to intersect a physical structure containing a plurality of items to be inventoried, and thus the scan trace can be overlaid over an image of the physical structure.
RFID readers usually offer improved efficiency over bar code scanning devices for retail inventory, by being capable of reading multiple RFID tags that are within range of the RF signal transmitted by an RFID reader. A downside to this multiple-read capability is lack of scanned items localization, due to insufficient correlation between where the RFID reader is located or oriented, and the RFID tags being read. Retail inventory management typically requires more than 90% of the RFID tags present in a department to be successfully acquired during the inventory process. When this high accuracy is not achieved, it is currently necessary to rescan the entire department, since the locations of any unread RFID tags are unknown.
When items are scanned using an RFID reader, the antenna of this device transmits a signal. The longevity of use of an EIR terminal with an RFID reader is impacted by the transmit power level utilized in scanning RFID tags. The distance at which an RFID tag may be read by an RFID reader is proportional to the transmit power level emitted by the RFID reader. Thus, an RFID reader using a higher transmit power level than required may have the unintended effect of unintentionally scanning RFID tags that are proximate to the tags that the user desires to scan.
A need exists for a method and system for reading RFID tags that conserves the power of the device and increases the accuracy when scanning select RFID tags.